A vehicle seat includes, in general, upholstered seat elements (seating portion and backrest) and a frame supporting the seat elements and mounting them to the vehicle. An upholstered seat element comprises a padding and trim material (e.g. textile, genuine or artificial leather, and the like) covering the padding and providing a durable outer surface for contact with a seat occupant. Typically, the padding is made from an expandable foam material, such as a polymer (e.g. polyurethane), and moulded to a predetermined shape during a moulding process. The trim cover is attached to the padding or the frame or both through an attachment assembly.
Such attachment assemblies exist in numerous variants. Generally, they comprise anchor components secured to the padding or the underlying seat frame, which the trim cover is fastened to, e.g. by means of hook elements, clamps, straps, or like fastening elements. Examples of attachment assemblies can be found, for instance, in US patent application 2005/0006944 A1, U.S. Pat. No. 6,817,675 and U.S. Pat. No. 4,865,383.
The areas of a vehicle seat wherein the attachment assemblies are located may be visible or hidden to the seat occupant, the visible variant being the more common one. The attachment areas (hereinafter referred to as “crimp channels”) may be recognisable, in the visible variant, as seam lines or grooves, defining and separating more loosely padded portions of the upholstered seat element. In the visible variant, the crimp channels contribute to a large extend to the outer appearance of the seat surface.
It is known that vehicle seats are increasingly equipped with various kinds of sensors and electronic devices, such as occupancy sensors, seat belt buckle sensors, seat heaters, etc. Integration of such devices into the seat is a complex process, in particular because of design constraints based upon haptic or aesthetic criteria. The course of the crimp channels represents a serious constraint for sensors and electronic devices, in particular if these are to be located close to or in the trim cover.
At crossings of a sheet-type electric device (such as e.g. film-type pressure sensors, film-type capacitive sensors, textile sensors, etc.) with a crimp channel, a deformation of the padding may cause buckling of the sheet type electric device. A conventional configuration of such a crossing is illustrated in FIGS. 1a-1c. The foam padding 10 has a channel 12 formed therein, which runs on the surface of the foam padding 10. A trim cover (not shown) is disposed on this surface of the padding and is secured thereto by an attachment assembly 14, 16 extending along the channel 12. It should be noted that the trim cover follows the contour of the padding surface and is drawn into the channel 12 by the attachment assembly 14, 16. A sheet-type sensor 18, sandwiched between the trim cover and the padding 10 is thus also urged into the channel 12 (FIG. 1b). FIG. 1a shows a top view of the crossing location. A portion of the sheet type sensor 18 crosses the channel 12 along the line A-A. To avoid too sharp bending of the sheet-type sensor 18 already in unloaded conditions, ramps 20, 22 have been formed in the wings of the channel 12 so as to provide for gentle bending of the sensor 18 at the crossing. When the upholstered element is subject to pressure (illustrated at reference numeral 26, exerted e.g. by a seat occupant), it is deformed whereby the geometry of the surface of the foam element 10 may change. This may cause the sheet-type sensor 18 to buckle at the crimp channel 12 (as shown at reference numeral 28 in FIG. 1c). Such buckling may deteriorate, in particular, the electric circuits of the sheet-type sensor 18, which is obviously undesirable.